Hornberg Castle was probably originally built in the late 12th century. The first mention of the castle dates from 1184. In 1259 lords of Hornberg sold the castle to the bishop of Speyer. Since 1612 it has been owned by the 12th generations of Gemmingen barons. Today the castle is a hotel.
Hornberg originally consisted of two separate castles. Between them was a bailey. Around 1510, both castles were enclosed together with the a common wall as an additional attachment of Conz Schott of Schottenstein.
The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.